Question about 2p2 Book Bindings For Mason (or others if they know)

[HotPockets]

A Whlie ago, Mason made a post pretaining to the type of glue used in the binding of 2p2 books. A PUR glue or something like that. I was just wondering around what time 2p2 started using this new glue. The reason being that my books take an absolute pounding and I'd prefer to get the editions that have the improved binding. I'm considering getting a new copy of ToP and 7CSFAP but I wasnt sure which editions and printings have the improved glue.